In the case of present-day couplings, such as quick-acting couplings, coaxial couplings, etc., it can sometimes be difficult for a user to couple the male and female parts of the coupling together when one of the parts is pressurised. The fluid may be air, gases, water, oils, greases, etc. When a coupling part is pressurised, the valve body, or main valve member, mounted in the coupling part has to be pushed in with great force in order to open a flow passage in the coupling part. Relief valves of various types are available, but these are often complicated and bulky and are sometimes not adequate for relieving high pressure. There is also a desire for couplings used often by workshop employees to be made user-friendly. There is also a need to provide couplings that can be used by persons having limited strength when one of the parts is pressurised. It is also desirable to provide a coupling that, purely from a safety point of view, will be coupled when one of the coupling parts is under high pressure. The coupling does not have to be limited to safety equipment, but can be applied to workshops, elderly care, hospitals, etc., where couplings are required in order to couple pressurised systems together.
U.S. Pat. No. 6,095,190 describes a coupling that attempts to solve the problem by easier coupling together of a pressurised female part and a male part. The solution is to provide three valves, namely a slide valve, a relief valve and a main valve, the valves opening in the aforementioned order upon coupling. A flexible ball valve is actuated by an actuator during the coupling operation and the excess pressure can be reduced.
U.S. Pat. No. 6,095,190 has an operating member in the form of a sleeve acting as a locking sleeve rotated into engagement with a stop in order to prevent unintended opening.